The overall objective of this project is to define the role of chemerin receptors CMKLR1 and CCRL2 in leukocyte trafficking, function, and the pathophysiology of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Preliminary results suggest that CMKLR1 is an integrin-triggering chemoattractant receptor expressed by macrophages, NK cells, and upregulated by activated dendritic cells;CCRL2 is a non-signaling chemerin "delivery" receptor expressed by mast cells, activated macrophages and endothelial cells that binds chemerin and serves to regulate the bioavailability of the attractant;and that the chemerin receptors play critical roles in modulating inflammatory responses in vivo. Studies under Aim 1 will determine if chemerin can induce CMKLR1-mediated integrin triggering and rapid adhesion in macrophages and NK cells. These studies will have important implications for understanding how CMKLR1 contributes to macrophages and NK trafficking in vivo where chemerin is activated by inflammation or coagulation-associated proteases. Studies under Aim 2 test the hypothesis that CCRL2 is a non-signaling chemerin "delivery" receptor that serves to concentrate and present active chemoattractant. These studies will elucidate the functional significance of CCRL2 in regulating chemerin activity and its signaling via CMKLR1 in vivo. Aim 3 will define the roles of CMKLR1 and CCRL2 in the pathophysiology of experimental autoimmune encephalomyelitis (EAE). Mice genetically deficient in CMKLR1 or CCRL2, as well as anti-mCMKLR1 blocking mAbs, will be used to investigate the contribution of these receptors to disease progression in animals. Local leukocyte infiltration, function, and cytokine production will be examined to define the mechanisms by which the receptors contribute to or modulate inflammation and immune responses in vivo. Together, the studies proposed promise to define a key regulatory mechanism in macrophage, mast cell, and NK cell biology and function. They may lead to novel targets or approaches for the prevention or treatment of autoimmune disease. PUBLIC HEALTH RELEVANCE: This research project has the potential to identify novel targets for the prevention and/or treatment of autoimmune diseases, such multiple sclerosis. This project will improve our understanding of white blood cell trafficking, and may offer new methods for therapeutically altering the accumulation and/or function of critical white blood cell populations at sites of tissue damage and inflammation.